Role of the Polymer Microstructure in Controlling Colloidal and Thermo-Responsive Properties of Nano-Objects Prepared Via RAFT Polymerization in a Non-polar Medium

After having demonstrated their potential in biomedicalapplications,thermo-responsive block copolymers that are able to self-assembleinto nano-objects in response to temperature modifications are becomingmore and more appealing in other sectors, such as the oil and gasand lubricant fields. Reversible addition-fragmentation chaintransfer (RAFT) polymerization-induced self-assembly has been demonstratedas a valuable strategy for producing nano-objects from modular blockcopolymers in non-polar media, required for the mentioned applications.Although the influence of the nature and size of the thermo-responsiveblock of these copolymers on the properties of the nano-objects isextensively studied in the literature, the role of the solvophilicblock is often neglected. In this work, we elucidate the role of themain microstructural parameters, including those of the solvophilicportion, of block copolymers produced by RAFT polymerization in thehydrocarbon blend decane/toluene 50:50 v/v on the thermo-responsivebehavior and colloidal properties of the resulting nano-objects. Twolong-aliphatic chain monomers were employed for the synthesis of fourmacromolecular chain transfer agents (macroCTAs), with increasingsolvophilicity according to the number of units (n) or length of the alkyl side chain (q). Subsequently,the macroCTAs were chain-extended with different repeating units ofdi(ethylene glycol) methyl ether methacrylate (p),leading to copolymers that are able to self-assemble below a criticaltemperature. We show that this cloud point can be tuned by actingon n, p, and q.On the other hand, the colloidal stability, expressed in terms ofarea of the particle covered by each solvophilic segment, is onlya function of n and q, which providesa way for controlling the size distribution of the nano-objects andto decouple it from the cloud point.